JP2003173757A - Ion beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the electron energy in a plasma while a plasma is emitted in a high frequency discharge plasma generating device, and thereby, further minimize the charged voltage of the substrate. <P>SOLUTION: This ion beam irradiation device comprises a plasma generating device 20 which, by generating a plasma 12 by high frequency discharge, supplies it in the vicinity of the upstream side of the substrate 4 and contains charging on the substrate surface resulting from irradiation of the ion beam 2. And the high frequency power source that supplies a high frequency power for generating a plasma to this plasma generating device 20 is made the high frequency power source 16a that outputs high frequency power 18 in the state in which amplitude modulation is applied on the original high frequency signal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam irradiation apparatus for irradiating a substrate with an ion beam to perform processing such as ion implantation, and more specifically, charging (charge-up) of a substrate during irradiation of the ion beam. ) To the improvement of the means to suppress.

[0002]

2. Description of the Related Art As one of means for suppressing charging of a substrate during ion beam irradiation, plasma emitted from a plasma generator is supplied to the vicinity of the substrate so that electrons in the plasma are irradiated with the ion beam. Conventionally, a technique used for neutralizing the positive charge associated with is proposed. This technique can supply low-energy electrons to the substrate as compared with the technique that uses primary electrons emitted from the filament and secondary electrons emitted by hitting it on an object, and thus negatively charges the substrate. Has the advantage of being small.

One of such plasma generators is a high frequency discharge type which uses high frequency discharge for plasma generation. Compared to the type that uses a filament to generate an electric discharge, this technique has a longer life, and (b) a lower gas pressure reduces the degree of vacuum in the processing chamber. Have advantages.

FIG. 9 shows a conventional example of an ion beam irradiation apparatus provided with such a high frequency discharge type plasma generator.

This ion beam irradiation apparatus is drawn out from an ion source (not shown) and, if necessary, mass separation,
In the vacuum container (processing chamber container) 8, the spot-shaped ion beam 2 subjected to acceleration or the like is subjected to an electric field or magnetic field in a fixed direction X (in this figure, the front and back directions of the surface,
This is horizontal, for example. The substrate (for example, semiconductor substrate) 4 held by the holder 6 while reciprocally scanning
And the substrate 4 is subjected to a treatment such as ion implantation.

The substrate 4 and the holder 6 are mechanically reciprocally scanned by a holder driving device 10 in a Y direction (for example, a vertical direction; the same applies hereinafter) substantially orthogonal to the X direction. By this and the above-mentioned scanning of the ion beam 2 (hybrid scanning), the entire surface of the substrate 4 is uniformly irradiated with the ion beam.

Plasma 1 is formed near the upstream side of the substrate 4.
2 is generated and supplied to the vicinity of the upstream side of the substrate 4,
A high frequency discharge type plasma generator 20 is provided which suppresses the charging of the surface of the substrate 4 due to the irradiation of the ion beam 2. The plasma generator 20 is attached to the outside of the vacuum container 8 located near the upstream side of the substrate 4 via an insulator 30 in this example.

This plasma generator 20 has a cylindrical plasma generation container 22, and a gas (for example, xenon gas) 14 introduced therein is high-frequency discharged by a high-frequency power 18 emitted from an antenna 28. To generate plasma 12 which is emitted by the plasma emission port 2
It has a structure to release from 4. Plasma generation container 22
A magnetic field for generating and maintaining the plasma 12 is applied to the inside from a magnetic coil 26 provided outside thereof in a direction along an axis 23 passing through the center of the plasma emission port 24.

The antenna 28 is supplied with high frequency power 18 from the high frequency power supply 16 through a matching circuit 19. Conventionally, the high frequency power 18 output from the high frequency power source 16 is a normal sine wave, that is, a sine wave continuous with a constant amplitude, and its frequency is, for example, 2.45 GHz or 13.5.
6 MHz.

When the substrate 4 is irradiated with the ion beam 2, the substrate 4 is left as it is due to the positive charge of the ion beam 2.
Surface is positively charged. In particular, when the surface is an insulator, it is easily charged. When the plasma 12 is supplied to the vicinity of the substrate 4 during the ion beam irradiation as described above, the electrons in the plasma 12 are attracted to the positively charged substrate surface and neutralize the positive charge. In principle, when the positive charge is neutralized, the electron attraction to the substrate 4 automatically stops. In this way, positive charging of the substrate surface due to ion beam irradiation can be suppressed.

[0011]

Although the principle of neutralization of positive charges associated with ion beam irradiation is as described above,
In reality, the substrate surface may be positively or negatively charged for the following reasons.

(1) When the ion beam 2 strikes the substrate 4 At this time, due to the positive charge by the ion beam 2 and the secondary electron emission from the substrate 4 due to the irradiation of the ion beam,
Although the surface of the substrate is positively charged, the electrons in the plasma 12 generated by the plasma generator 20 cause the electrons to be, for example, a beam plasma (the ion beam 2 does not actually consist of only ions, but takes in electrons from the surroundings). It is in a plasma state by doing the same, and say that)
Are taken into the substrate 4 and move toward the substrate 4 to neutralize the positive charge and alleviate the charge. This degree of relaxation depends on the plasma generator 2
It depends on the electron density and the electron energy in the plasma 12 from 0, and generally, the former is larger and the latter is smaller, the relaxation degree is larger. This is because the lower the energy of the electrons, the easier the electrons are taken into the beam plasma from the plasma 12 from the plasma generator 20.

(2) When the ion beam 2 does not hit the substrate 4, the ion beam 2 is normally scanned to the outside of the substrate 4 (overscan). The substrate 4 is also scanned in the Y direction as described above. Therefore, the plasma generator 20
While the plasma 12 is being emitted from the ion beam 2
May not hit the substrate 4. At this time, the substrate 4 is the plasma 1 emitted from the plasma generator 20.
Will be exposed to 2. The charging voltage of the substrate surface at this time is determined by the balance between the amount of electrons and the amount of ions in the plasma 12 and the energy of the electrons. Since electrons are generally lighter and have higher mobility, the charging voltage at this time becomes negative. For example, when there are almost no ions near the substrate 4, the charging voltage rises to a voltage corresponding to the maximum energy of electrons in the plasma 12.

As can be seen from the above, in order to reduce the positive or negative charging voltage of the substrate 4, in particular, to reduce the negative charging voltage, it is necessary to reduce the electron energy in the plasma 12.

According to the high frequency discharge type plasma generator 20, as compared with the technique using the primary electron emitted from the filament or the secondary electron emitted by hitting the primary electron on the object as described above, the energy consumption is lower. However, in recent years, semiconductor devices have been miniaturized and it is necessary to suppress the charging voltage during ion implantation to a smaller level. Technology is not always enough.

That is, the high frequency discharge type plasma generator 2
Even if it is zero, electrons are easily accelerated by the high-frequency electric field at the time of plasma generation, so that electrons with high energy are easily generated. When an ECR (electron cyclotron resonance) discharge, which is a form of high-frequency discharge, is used to increase the plasma density, the electron cyclotron resonance accelerates the electrons, resulting in the generation of higher energy electrons. Easy to be affected. Therefore, the negative charging voltage on the substrate surface tends to increase.

In this case, if the power of the high frequency power 18 supplied to the plasma generator 20 is narrowed down, the plasma 1
Although the electron energy in 2 decreases, plasma 1
Since the density of No. 2 decreases and the plasma 12 disappears, it is not possible to effectively suppress the charging of the substrate 4 simply by reducing the power of the high frequency power 18.

Therefore, according to the present invention, the electron energy in the plasma can be reduced while the plasma is kept on in the high frequency discharge type plasma generator.
It is a main object of the present invention to provide an ion beam irradiation device that can further reduce the charging voltage of the substrate.

[0019]

In a first ion beam irradiation apparatus according to the present invention, a high-frequency power supply for supplying high-frequency power to a high-frequency discharge type plasma generator as described above is used as an original high-frequency signal. It is characterized in that it is a high frequency power source that outputs high frequency power in a modulated state.

In the high frequency discharge type plasma generator, the electrons in the plasma are accelerated by the high frequency power. The acceleration depends on the strength of the high frequency electric field applied to the plasma, that is, the strength of the high frequency power. Decided. However, in reality, electrons are generated while colliding with neutral particles in the plasma (gas introduced into the plasma generator),
Since acceleration, deceleration, and annihilation are repeated, the electrons are not accelerated indefinitely, but have a certain energy distribution even in the continuous wave mode in which the intensity of the high-frequency power is constant as in the conventional case. Become.

On the other hand, if the intensity of the high frequency power is reduced to near 0 before the electrons in the plasma are accelerated to high energy, the electrons will not be accelerated any further. That is, by repeating the high frequency power in the high power state and the state near 0, the electron energy distribution becomes lower than that in the continuous wave mode.

In this case, the strength of the high frequency power is instantaneously reduced to 0.
It was confirmed by the inventor of the present application that plasma is not extinguished immediately when it is changed (decreased) to the vicinity, but the plasma does not disappear immediately.

For example, the frequency of the high frequency power is 2.45G.
Hz, output 100 W, introduced xenon gas flow rate 0.2
When the amount of electrons emitted from the plasma generator when the high frequency power was turned on and off under the condition of ccm was measured,
It was confirmed that the plasma reached a steady state about 60 μs after the high frequency power was turned on, and the plasma decayed and disappeared over a period of about 30 μs after the high frequency power was turned off.

From this result, the strength of the high frequency power supplied to the plasma generator is repeated at a predetermined cycle between a relatively high power state and a relatively low power state (for example, near 0). Thus, the inventor of the present application has found that the electron energy in the plasma can be reduced while the plasma is turned on. Due to this decrease in electron energy, the charging voltage of the substrate can be made smaller.

To change the strength of the high-frequency power as described above, the present invention uses a high-frequency power source that outputs high-frequency power in the modulated wave mode in which the original high-frequency signal is amplitude-modulated. Can be realized by

A second ion beam irradiation apparatus according to the present invention comprises a high frequency power source for supplying high frequency power to the high frequency discharge type plasma generator as described above, and a continuous wave mode for outputting high frequency power of constant amplitude. A high frequency power source capable of switching to a modulation wave mode for outputting high frequency power in a state where amplitude modulation is applied to an original high frequency signal, and the mode of the high frequency power source is set to the continuous mode when plasma is ignited in the plasma generator. It is characterized in that a control device is provided for controlling the wave mode and switching to the modulated wave mode after ignition of the plasma.

Even in the modulated wave mode as described above, plasma can be ignited in the plasma generator, but during plasma ignition, continuous wave mode does not have a period in which the plasma density lowers, so that the plasma can be more easily ignited. The ignition can be performed reliably.

Therefore, by adopting the structure for mode switching as in the second ion beam irradiation apparatus, the ignition of the plasma in the plasma generation apparatus becomes easier and more reliable. Moreover, after plasma ignition, the electron energy in the plasma can be reduced while the plasma is still lit, so that the same effect as the first ion beam irradiation apparatus can be obtained.

[0029]

1 is a side view showing an example of an ion beam irradiation apparatus according to the present invention. 2 is shown in FIG.
It is sectional drawing which follows the line CC of FIG. The same or corresponding parts as those of the conventional example shown in FIG. 9 are denoted by the same reference numerals, and the differences from the conventional example will be mainly described below.

First, the structure of the plasma generator 20 will be described. In this example, the plasma generating container 22 has a cylinder extending in the direction of the ion beam 2 along the scanning direction X with the axis 23 as a long tube. It has a shape. A gas introduction pipe 40 for introducing the gas 14 and the antenna 28 are attached to both ends of the plasma generation container 22, respectively. The plasma emission port 24 extends long along the shaft 23. With such a structure, it is possible to generate the plasma 12 having a long width in the scanning direction X of the ion beam in the plasma generation container 22 and to discharge the plasma 12 having such a long width from the plasma emission port 24. Even if the ion beam 2 is scanned in the X direction, the plasma 12 can be uniformly supplied to the vicinity of the scanned ion beam 2. As a result, it is possible to uniformly suppress the charging on the surface of the substrate 4,
It is possible to suppress the generation of a portion having a large charging voltage.

Outside the plasma generating container 22, one or more magnets 3 for generating a magnetic field 38 in the direction along the axis 23.
6 is provided. The magnet 36 is typically a permanent magnet. By this magnetic field 38, the plasma generator 20
Since the ions in the plasma 12 emitted from the substrate 12 are bent toward the substrate and guided to the substrate 4 to increase the amount of ions supplied to the substrate 4, the ion beam 2 does not hit the substrate 4 as described above. However, even if the plasma 1 is used in a state where it may occur, negative charge due to electrons in the plasma 12 emitted from the plasma generator 20 is generated.
It can be successfully neutralized by the ions in 2. As a result, the effect of reducing the charging voltage on the substrate surface can be further enhanced by suppressing the charging on the substrate surface.

The ECR condition may be satisfied in the plasma generating container 22 by the magnetic field generated by the magnet 36, and this condition is satisfied in this example. For example, when the fundamental frequency of the high frequency power 18 is 2.45 GHz,
If a magnetic field of 875 × 10 ⁻⁴ Tesla is generated in the plasma generation container 22, the ECR condition is satisfied, so that the ECR discharge can be generated. As a result, the plasma 12
It is possible to further improve the production efficiency of.

Next, the high frequency power source will be described. In this example, the conventional normal high frequency power source 16 described in FIG. 9 is used.
Instead of high frequency, the high frequency power 18 in the state where the original high frequency signal is amplitude-modulated is output and supplied to the plasma generator 20 (more specifically, its antenna 28) through the matching circuit 19. The power supply 16a is provided.

An example of the structure of the high frequency power source 16a is shown in FIG.
Shown in. The high frequency power supply 16a includes a high frequency oscillator 52 that generates an original high frequency signal (also referred to as a carrier wave) 53, a modulator 54 that amplitude-modulates the high frequency signal 53 and outputs a high frequency signal 55, and this modulation. Bowl 54
A modulation signal generator 58 for supplying a modulation signal 59 for modulation to
And a high frequency amplifier 56 that amplifies the high frequency signal 55 output from the modulator 54 to a required output (power) and outputs the high frequency power 18. High frequency oscillator 52
The frequency f of the high frequency signal 53 output from
2.45 GHz, 13.56 MHz, etc. That is, in this specification, high frequency is a broad concept including microwaves. The fine vertical lines in FIGS. 4 to 6 indicate the high-frequency signal 53.
Shows the vibration of.

In this example, the high frequency power supply 16a can be switched between a continuous wave mode for outputting the high frequency power 18 having a constant amplitude and a modulation wave mode for outputting the high frequency power 18 in the amplitude-modulated state. In other words, the state in which the amplitude modulation is performed is a state in which a relatively large output (amplitude) state and a relatively small output (amplitude) state are repeated in a constant cycle. In this example, this switching is performed by switching the waveform of the modulation signal 59 output from the modulation signal generator 58. That is, the continuous wave mode can be set by setting the modulated signal 59 as a continuous wave having a constant amplitude, and the modulated signal 59 can be modulated by forming a predetermined waveform (for example, a cosine wave, a triangular wave, a rectangular wave described later). Can be switched to wave mode.

In this example, a control device 50 for controlling the high frequency power source 16a and controlling the modulation waveform, the modulation period T, the amplitude A, the duty ratio d in the case of a rectangular wave, etc. of the high frequency power 18 output from the high frequency power source 16a is provided. ing. More specifically,
The control device 50 gives command information to the modulation signal generator 58, and controls the waveform of the modulation signal 59 output therefrom, the period T, the duty ratio d in the case of a rectangular wave, and the like. Further, the control device 50 gives command information to the high frequency amplifier 56 to control the amplitude A of the high frequency power 18 output therefrom.

In this example, the control device 50 further sets the mode of the high frequency power source 16a, that is, the high frequency power source 1a.
It has a function of controlling the mode of the high frequency power 18 output from 6a to a continuous wave mode when the plasma 12 in the plasma generator 20 is ignited and to a modulated wave mode after the plasma 12 is ignited.

Examples of the waveform of the high frequency power 18 output from the high frequency power supply 16a in the modulated wave mode are shown in FIGS.

FIG. 4 shows an example of the waveform of the high frequency power 18 modulated in a sine wave. This high frequency power 18 is
Can be expressed by a function F (t) of Here, f is the frequency of the high frequency signal 53, t is time, G (T, t) is a function (modulation function) representing the modulated signal 59, T is its period (modulation period), and A is the amplitude. . The modulation cycle T is generally sufficiently larger than the cycle (1 / f) of the high frequency signal 53.

[0040]

## EQU1 ## F (t) = G (T, t) .sin2.pi.ft G (T, t) = (A / 2) {1-cos2π (t / T)}

FIG. 5 shows an example of the waveform of the high frequency power 18 modulated in the triangular wave shape. This high frequency power 18 is
Can be expressed by a function F (t) of Here, n is an integer.

[0042]

[Equation 2]   F (t) = G (T, t) · sin2πft   G (T, t) = (2A / T) · (t−nT) ... nT ≦ t <(n + 1/2)                 When T               = A {1- (t-nT) / T} (n + 1/2) T≤t <(                 When n + 1) T

FIG. 6 shows an example of the waveform of the high frequency power 18 modulated into a rectangular wave. In this case, the state of the amplitude A and the state of 0 are alternately repeated. This high frequency power 18
Can be expressed by the function F (t) of Equation 3. here,
d is a duty ratio, which is represented by d = t ₀ / T when the period of the amplitude A (ON period) is t _0, and normally 0 to 1
Takes a value up to.

[0044]

[Equation 3]   F (t) = G (T, t) · sin2πft   G (T, t) = A ... When nT ≦ t <(n + d) T               = 0 ... (n + d) ≦ t <(n + 1) T

In the high frequency power 18 of each of the above waveforms, the amplitude at the minimum amplitude may be a value near 0 instead of being completely set to 0 as in the above examples. In addition, the value may be set to a value at which the lighting of the plasma 12 in the plasma generator 20 can be maintained at a minimum (this is smaller than the amplitude A).

The waveform of the high frequency electric power 18 in the modulated wave mode is not limited to the examples shown in FIGS. 4 to 6 but may be other waveforms. For example, the modulation function G (T, t) shown in equation 1 and the modulation function G (T, t) shown in equation 2
A waveform represented by a modulation function obtained by multiplying by, that is, a waveform obtained by combining a sine wave and a triangular wave may be used. However, in any of the waveforms, it is necessary that the portion having a relatively large amplitude and the portion having a relatively small amplitude be repeated in a constant cycle.

From the viewpoint of the high frequency power source 16a, it is the simplest to output the rectangular wave as shown in FIG. 6 among the various waveforms as described above. Therefore, high frequency power 1
It can be said that it is most realistic to make the waveform of 8 into a rectangular waveform.

When the continuous wave mode high frequency power 18 is output from the high frequency power supply 16a, it can be considered that the modulation function G (T, t) in the above equations 1 to 3 is always A.

Using the high frequency power source 16a as described above,
The strength of the high-frequency power 18 supplied to the plasma generator 20 is repeated at a predetermined cycle between a relatively high power state and a relatively low power state (for example, near 0), so as to be described above. As described above, the electron energy in the plasma 12 can be reduced while the plasma 12 is prevented from extinguishing and the plasma 12 is kept on. Due to this decrease in electron energy, the charging voltage of the substrate can be made smaller. Thereby, for example, the dielectric breakdown of the semiconductor device during the irradiation of the ion beam can be prevented, and the yield of the semiconductor device manufacturing can be improved. Further, it is possible to cope with miniaturization of semiconductor devices.

In particular, when the ECR discharge is used, the electrons are likely to be accelerated to a higher energy by the electron cyclotron resonance as described above. Therefore, by using the high frequency power 18 in the modulated wave mode as described above,
The effect of reducing the electron energy in the plasma 12 is great.

Further, the power consumed by the high-frequency power supply 16a is smaller than that in the case of using the conventional high-frequency power supply 16 which continuously outputs high-frequency power having a constant amplitude, so that energy saving of the device and running cost reduction can be achieved. You can

Further, even in the modulated wave mode as described above, the plasma 12 can be ignited in the plasma generator 20, but in the plasma ignition, the continuous wave mode has no lowering period of the plasma density. The plasma 12 can be ignited more easily and reliably.

Therefore, as in this example, the high frequency power source 16
By adopting a configuration for switching the mode of the high frequency power 18 output from a, the plasma generator 2
Ignition of the plasma 12 at 0 becomes easier and more reliable. Moreover, after plasma ignition, it is possible to obtain the same effects as the above by using the modulated wave mode. That is, the electron energy in the plasma 12 can be reduced while the plasma 12 is kept on.
In addition, it is possible to save energy of the device and reduce running costs.

By the way, the high frequency power 1 in the modulated wave mode 1
If the modulation cycle T of 8 is too long, the high frequency power 18
Since the period in which the voltage is not applied becomes long, the plasma 12 may be extinguished in the plasma generator 20. On the contrary, if the modulation cycle T is made too short, the high frequency power 18 will be supplied again immediately before the electron energy in the plasma 12 drops.
Is applied, the effect of lowering electron energy in the plasma 12 is diminished.

Therefore, when the preferable range of the modulation period T is roughly considered, as described above, the high frequency power 1
When the off period 8 (or a period below the threshold value at which the plasma 12 can be kept on) is about 30 μs or more, the plasma 12 is extinguished. When this 30 μs is converted to the modulation period T, it doubles to 60 μs, but since there is no margin at all with this, the modulation period T
Is preferably about 50 μs or less. The lower limit of the modulation period T is, for example, 20% of the maximum, and is preferably about 10 μs or more. From the above, when a schematic preferable range of the modulation period T is shown, it becomes the formula 4, which is expressed by the modulation frequency f
_When expressed by _M (= 1 / T), the equation 5 is obtained.

[0056]

[Equation 4] 10 ≦ T ≦ 50 [μs]

[0057]

[Equation 5] 20 ≦ f _M ≦ 100 [kHz]

In the ion beam irradiation apparatus shown in FIGS. 1 and 2, when the high frequency power 18 which is modulated in a rectangular wave is used, the experimental result of the preferable range of the modulation period T of the rectangular wave and the duty ratio d is shown below. Explained.

FIG. 7 shows the negative charging voltage observed in the vicinity of the substrate 4 when the modulation frequency f _M is changed with the duty ratio d fixed at 0.5. In this portion, when the ion current and the electron current from the plasma 12 are compared, the electron current is overwhelmingly larger, and thus the measured voltage value is almost equal to the maximum electron energy. At the time of this measurement, the fundamental wave frequency of the high frequency power 18 (that is, the frequency f of the high frequency signal 53) is 2.45 GHz, and the high frequency power 1
The peak power of No. 8 (that is, the amplitude A in FIG. 6) was 100 W, and the flow rate of the introduced xenon gas 14 was 0.2 ccm.

As can be seen from FIG. 7, the modulation frequency f_MBut
The charging voltage is smallest around 30 kHz. This
The reason for this is as follows. That is, the modulation frequency
Number f _MNear 10 kHz (modulation cycle T is 100 μ
s), the high frequency power 18 is on and off
Since all the intervals are about 50 μs, as described above.
In addition, the plasma 12 is repeatedly turned on and off, and is turned on again.
In the continuous wave mode as well, the plasma 12 is in a steady state.
It is close to the continuous wave mode near this frequency.
The same high electron energy has been observed. Plas
Considering the operation of the generator 20, in the vicinity of this frequency
Will include the time when the plasma 12 is turned off.
The electron supply from the plasma 12 to the substrate 4 becomes zero.
Therefore, it is not possible to adopt around this 10 kHz.

When the modulation frequency f _M is increased from 10 kHz, the plasma 12 is gradually turned on. In this state, the on period of the high frequency power 18 becomes shorter, and when the high frequency power 18 is turned off, the electrons are decelerated while colliding with the neutral particles in the plasma 12, and low energy electrons are generated, whereby a negative charging voltage is generated. Becomes smaller.

On the other hand, when the modulation frequency f _M exceeds 30 kHz, the negative charging voltage tends to increase again. Although this mechanism is not well understood at present, it is presumed that the deceleration time of electrons due to turning off the high frequency power 18 is shortened.

In any case, since the electron energy in the plasma 12 changes depending on the magnitude of the modulation frequency f _M , and the negative charging voltage also changes accordingly, the modulation frequency f _M
It was also confirmed by experiments that there is a preferable range for. For example, if the maximum value of the charging voltage required when ion beam irradiation (ion implantation) is performed on the semiconductor device on the surface of the substrate 4 is 8 V, as shown in FIG. 7, the preferable range of the modulation frequency f _M is , Duty ratio d
Is 0.5, the range is 25 kHz to 80 kHz.

The modulation frequency f _M is changed, that is, the length of the ON period and the OFF period of the high frequency power 18 is changed, and this can be realized by changing the duty ratio d in the rectangular wave. it can. For example, FIG. 8 shows the negative charging voltage observed in the vicinity of the substrate 4 when the modulation frequency f _M is fixed at 50 kHz and the duty ratio d is changed. It can be seen that the charging voltage gradually increases as the duty ratio d increases. Similarly to the above, when the maximum value of the charging voltage is 8 V, the duty ratio d in this case is preferably 0.7 or less. However, if the duty ratio d is made too small, the density of the plasma 12 decreases, so the duty ratio d is preferably 0.3 or more. That is, the preferable range of the duty ratio d is a range of 0.3 to 0.7 when the modulation frequency f _M is 50 kHz.

When the modulation frequency f _M and the duty ratio d in the case of a rectangular wave are summed up, under the above-mentioned conditions, the modulation frequency f _M is within the preferable range as described above.
_M is set to about 30 to 50 kHz, and the duty ratio d is set to 0.
It can be said that it is more preferable to set it to about 4 to 0.5.

It should be noted that, as in the example shown in FIG. 2, a negative or positive extraction voltage V _E may be applied to the plasma generation container 22 from a DC extraction power source 42. By doing so, the amount of ions and the amount of electrons in the plasma 12 emitted from the plasma generation device 20 can be controlled by the magnitude and polarity of the extraction voltage V _E , whereby the surface of the substrate is charged. You can control the situation.

The plasma generator 20 is shown in FIGS.
Although the structure shown in FIG. 9 is preferable for the above reason, the structure is not limited thereto, and the structure shown in FIG. 9 and other structures may be used.

The plasma generator 20 uses the ion beam 2
It may be provided in the vacuum container 8 in order to bring it closer.
Alternatively, the plasma generator 20 may be provided in a cylinder inserted into the vacuum container 8. By doing so, it is possible to more effectively supply the plasma 12 to the ion beam 2 and the beam plasma containing the ion beam from nearer, and to use the plasma 12 more effectively by suppressing charging.

The inner wall of the plasma generating container 22 has metal contamination due to sputtering of the plasma 12 and the antenna 30.
It may be covered with an insulating material in order to prevent the conductive sputtered material from adhering thereto.

[0070]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, since the high-frequency power source as described above is provided, it is possible to reduce the electron energy in the high-frequency discharge type plasma generator while the plasma is turned on. You can As a result, the charging voltage of the substrate can be made smaller.

Further, as compared with the conventional case of using a high frequency power source which continuously outputs a high frequency power of a constant amplitude, the power consumed by the high frequency power source is reduced, and the energy saving of the device and the running cost can be reduced. .

According to the second aspect of the present invention, since the high frequency power supply and the control device as described above are provided and the high frequency power at the time of plasma ignition in the plasma generator is set to the continuous wave mode, the plasma ignition is performed. Will be easier and more reliable. Moreover, since the high frequency power after plasma ignition is switched to the modulated wave mode, after plasma ignition, the same effect as the invention according to claim 1 can be obtained.

[Brief description of drawings]

FIG. 1 is a side view showing an example of an ion beam irradiation apparatus according to the present invention.

2 is a cross-sectional view taken along the line CC of FIG.

FIG. 3 is a diagram showing an example of a configuration of a high frequency power supply in FIG.

FIG. 4 is a diagram showing an example of a waveform of high-frequency power modulated in a sine wave shape.

FIG. 5 is a diagram showing an example of a waveform of high frequency power modulated in a triangular wave shape.

FIG. 6 is a diagram showing an example of a waveform of high-frequency power modulated into a rectangular wave shape.

FIG. 7 is a diagram showing an example of a result of measurement of a relationship between a modulation frequency of a high frequency power modulated in a rectangular wave shape and a negative charging voltage observed near the substrate.

FIG. 8 is a diagram showing an example of a result of measuring a relationship between a duty ratio of a high frequency power modulated in a rectangular wave shape and a negative charging voltage observed near the substrate.

FIG. 9 is a side view showing an example of a conventional ion beam irradiation apparatus.

[Explanation of symbols]

2 ion beam 4 substrates 12 plasma 16a high frequency power supply 18 High frequency power 20 Plasma generator 50 controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05H 1/46 H01L 21/265 N

Claims (2)

[Claims] 1. An ion beam irradiation device for irradiating a substrate with an ion beam for processing, wherein plasma is generated by high-frequency discharge and the plasma is supplied near the upstream side of the substrate for ion beam irradiation. In an ion beam irradiation apparatus equipped with a plasma generator that suppresses electrification of a substrate surface that accompanies it, and a high-frequency power supply that supplies high-frequency power for plasma generation to the plasma generator, the high-frequency power supply is applied to an original high-frequency signal. An ion beam irradiation apparatus, which is a high-frequency power source that outputs high-frequency power in a modulated state. 2. An ion beam irradiation apparatus for irradiating a substrate with an ion beam for processing, wherein plasma is generated by high-frequency discharge and the plasma is supplied near the upstream side of the substrate for ion beam irradiation. An ion beam irradiation apparatus comprising: a plasma generator that suppresses electrification of a substrate surface, and a high-frequency power source that supplies high-frequency power for plasma generation to the plasma generator, wherein the high-frequency power source outputs high-frequency power with a constant amplitude. A continuous wave mode for switching between a continuous wave mode and a modulated wave mode for outputting a high frequency power in a state where the original high frequency signal is amplitude-modulated, and the mode of the high frequency power source is the plasma in the plasma generator. The control is such that the continuous wave mode is set at the time of ignition and the modulation wave mode is set after the plasma is ignited. An ion beam irradiation device, which is equipped with a control device.